#include "bits/stdc++.h"
using namespace std;
#define ll long long int

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    string s,t;
    int l;
    cin >> s;
    t=s;
    l=s.length();
    if (l%2==1) cout << "NO" << endl;
    else {
        s.erase(l/2,l-1);
        if (t==s+s) cout << "YES" << endl;
        else cout << "NO" << endl;
    }
    return 0;
}